The invention relates to a method of manufacturing a cathode ray tube comprising an electron gun having electrodes.
Cathode ray tubes are used, inter alia, in television receivers, computer monitors and oscilloscopes.
Cathode ray tubes of the type mentioned in the opening paragraph comprise an electron gun having electrodes. In the electron gun one or more electron beams are generated. In operation, electro-optical fields are generated by means of electrodes having apertures for allowing passage of the electron beam(s). The electron beams are accelerated and focused by means of said fields. High voltages (above approximately 10 kV) voltages are applied to some electrodes. In particular in cathode ray tubes having a high picture quality, for example so-called HDTV display tubes or display tubes for High-Res (high resolution) computer monitors there is a tendency to apply ever increasing voltages to the electrodes. Such high voltages cause a number of problems, hereinafter referred to as "high-voltage behaviour". Electron sparks may hop between electrodes, the so-called "flashover". Such sparks may damage the display tube, cause loose parts in the display tube and/or adversely affect the life of the display tube. Under certain conditions this phenomenon also leads to a disturbing ticking or crackling noise. It is also possible that electrons are emitted from an electrode, the so-called "blue glow". These electrons adversely affect the contrast of the image displayed on the display screen. This also causes leakage currents between the electrodes. In operation, these leakage currents cause fluctuations of the electronic voltage between the electrodes and hence fluctuations of the image displayed.